Method and apparatus for detecting liner slips

ABSTRACT

The present invention refers to a method and apparatus ( 1 ) for detecting liner slips in a milking machine which involves, for each milking unit, a clawpiece and a cluster of teat cups connected to the clawpiece, wherein each teat cup has a rigid shell body and an internal flexible liner, the liner comprising a mouthpiece and a body part, whereby the liner extends through the bottom of the shell body as a short milk tube and is connected to the clawpiece and further, by way of a long milk tube, to a source of steady vacuum, while the annular space, between the teat cup shell body and the teat cup liner, is connected to the clawpiece by a pulse tube and further to a source of pulsating vacuum. Alternatively, each liner in the system is connected to the vacuum source by way of a respective individual long milk tube, wherein the clawpiece is omitted. The invention includes continuously or discontinuously sensing the pressure in the system downstream of said long milk tube(s), and detecting a liner slip in dependence of a predetermined change in said sensed pressure.

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to dairy farm machine milkingand particularly to a method and an apparatus for detecting liner slipsduring machine milking, i.e. when the liner slips on the teat of ananimal due to air leaking past the teat and the liner.

DESCRIPTION OF RELATED ART AND BACKGROUND OF THE INVENTION

In modern dairy farm industry there are continuous research anddevelopment activities in order to improve the efficiency of milkingmachines, which, inter alia, involves increased milk yield, reducedmilking time, while still maintaining good udder health.

One of the parameters in this respect is the presence of liner slips.These slips, that occasionally appear, may affect, i.e. increase theoccurrence of udder infections, which results in a deteriorated milkquality. Besides, many liner slips produce an irritating noise, and ifthe slip is large the milking equipment may even fall off the animal.Thus, milking equipment should be designed to introduce as few linerslips as possible, and preferably no liner slips at all. Therefore, thenumber of liner slips is monitored during development and testing ofdifferent equipment.

Manual counting of liner slips by virtue of listening for the noise thatthey cause have been performed at test farms, but such a method is timeconsuming, labor intensive, costly, and to a certain degree unreliableas one has to rely on the human perception.

Attempts have been made to solve the problem of the lack of a reliableliner slip measuring system using some different approaches.

Measuring increased air flow through the system as a measure of thedegree of liner slip is disclosed by G. A. Mein et al. in Air leakagepast the teat and teatcup liner during milking, Aus. J. Dairy Tech.,March 1973 and by E. J. O'Callaghan in Measurement of liner slips,milking time and milk yield, J. Dairy Sci. 79:390, 1995. A liner slipwas defined by O'Callaghan as an air inlet larger than 35 l/min.Drawbacks associated with this method includes, inter alia,time-demanding re-calibration during the measurement and the requirementof voluminous equipment.

Measuring the vacuum drop in the claw was proposed by S. B. Spencer andC. Volz in Measuring milking machine liner slips, J. Dairy Sci. 73:1000,1989. They suggested a vacuum drop of 8 kPa in less than 0.25 seconds asa criterion for a liner slip. Subsequent to a detected liner slip, thedetector was blocked during five seconds in order not to detectsubsequent fluctuations, that might occur, as a further liner slip. Thisapproach may, however, not always provide adequate protection frommechanical damage of the measuring equipment; for instance externalelectric connection cables to the claw will be needed, which furtherinfers that it may not operate satisfactorily in the long run. Theapproach also puts restrictions on the size of the sensor to beemployed.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amethod for detecting liner slips in a milking machine which involves,for each milking unit, a clawpiece and a cluster of teat cups connectedto the clawpiece, wherein each teat cup has a shell body and an internalflexible liner, said liner comprising a mouthpiece and a body part,whereby the liner extends through the bottom of the shell body as ashort milk tube and is connected to the clawpiece and further, by way ofa long milk tube, to a source of steady vacuum, while the annular space,between the teat cup shell body and the teat cup liner, is connected tothe clawpiece by a pulse tube and further to a source of pulsatingvacuum, which avoids at least some of the problems discussed above.

It is in this respect a particular object of the invention to providesuch a method that is effective, accurate, reliable, easy to install andmaintain, and particularly of a low cost.

It is yet a further object of the invention to provide the method insuch a way that it is easily reconfigurable to meet changing demands.

These objects among others are, according to one aspect of theinvention, fulfilled by a method wherein a milking machine system isprovided, the milking machine system having at least one milking unit.Each of the milking units include a clawpiece and a cluster of teat cupsconnected to the clawpiece, each of the teat cups having a shell bodyand an internal flexible liner. The liner includes a mouthpiece and abody part whereby the liner extends through the bottom of the shell bodyas a short milk tube and is connected to a source of steady vacuum byway of a long milk tube. An annular space is located between the teatcup shell body and the teat cup liner, the annular space being connectedto the clawpiece by a pulse tube and further to a source of pulsatingvacuum. The method includes the steps of sensing the pressure in thesystem downstream of the long milk tube and the step of detecting aliner slip in dependence of a predetermined change in the sensedpressure.

A further object of the present invention is to provide an apparatus forperforming the method according to the first aspect of the invention.

In this respect, it is yet a further object of the invention to beintegratable in existing machine milking systems.

Consequently, there is according to a second aspect of the presentinvention provided an apparatus for use in a milking machine having atleast one milking unit. Each of the milking units include a clawpieceand a cluster of teat cups connected to the clawpiece, each of the teatcups having a shell body and an internal flexible liner. The linerincludes a mouthpiece and a body part whereby the liner extends throughthe bottom of the shell body as a short milk tube and is connected to asource of steady vacuum by way of a long milk tube. An annular space islocated between the teat cup shell body and the teat cup liner, theannular space being connected to the clawpiece by a pulse tube andfurther to a source of pulsating vacuum. The apparatus includes apressure sensor located downstream of the long milk tube forcontinuously or discontinuously sensing the pressure in the systemdownstream of the long milk tube and a detector connected to the sensorarranged for detecting a liner slip in dependence of a predeterminedchanged in the sensed pressure.

Yet a further object of the present invention is to provide a method fordetecting liner slips in a milking machine system which involves, foreach milking unit, teat cups, each having a shell body and an internalflexible liner, said internal flexible liner comprising a mouthpiece anda body part, wherein each liner extends through the bottom of therespective shell body and is connected, by way of a respective long milktube, to a source of steady vacuum, while the respective annular space,between the shell body and the liner, is connected to a source ofpulsating vacuum, which exhibits the above said characteristics.

Accordingly, there is according to a third aspect of the presentinvention provided a method for detecting liner slips in a milkingmachine system having at least one milking unit, each of the milkingunits including a plurality of teat cups and each of the teat cupshaving a shell body and an internal flexible liner. The internalflexible liner includes a mouthpiece and a body part, wherein each linerextends through the bottom of the respective shell body and isconnected, by way of a respective long milk tube, to a source of steadyvacuum. A respective annular space, located between the shell body andthe liner is connected to a source of pulsating vacuum. The method ofthis third aspect includes the steps of sensing the pressure in thesystem downstream of the long milk tubes, and detecting a liner slip independence of a predetermined change in the sensed pressure.

Finally, an object of the invention is to provide an apparatus forperforming the method according to the third aspect of the invention andhence, an apparatus is provided for detecting liner slips in a milkingmachine system having at least one milking unit. Each milking unit has aplurality of teat cups, each having a shell body and an internalflexible liner, the internal flexible liner including a mouthpiece and abody part. Each liner extends through the bottom of the respective shellbody and is connected, by way of a respective long milk tube, to asource of steady vacuum. An annular space is located between the teatcup shell body and the teat cup liner and is connected to a source ofpulsating vacuum. The apparatus includes a pressure sensor locateddownstream of the long milk tubes for continuously or discontinuouslysensing the pressure in the system downstream of the long milk tubes,and a detecting means connected to said sensor arranged for detecting aliner slip in dependence of a predetermined change in the sensedpressure.

An advantage of the present invention is that while its sensor isimplemented downstream of the long milk tube(s), it is protected frommechanical stress and no electric connections or the like isnecessitated upstream of this point, which provides a reliable operationof the same.

Further characteristics of the invention and advantages thereof will beevident from the following detailed description of embodiments of theinvention, which are shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description of embodiments of the present invention givenhereinbelow and the accompanying FIGS. 1-4 which are given by way ofillustration only, and thus are not limitative of the invention.

FIG. 1 displays schematically an apparatus for detecting liner slipsaccording to an embodiment of the present invention.

FIG. 2 illustrates diagrammatically the vacuum level as a function oftime during a typical liner slip wherein various detection criteria asused in the present invention are indicated.

FIG. 3 illustrates diagrammatically vacuum levels as measured during aninduced liner slip at various points in a milking machine in which thepresent invention may be employed.

FIG. 4 displays four strip chart recordings of the vacuum level in theclaw of the milking machine during occurrence of liner slips, all ofwhich were detected as liner slips by the liner slip detecting apparatusaccording to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set fourth, such as particularhardware, applications, techniques, etc. in order to provide a thoroughunderstanding of the present invention. However, it will be apparent toone skilled in the art that the present invention may be practiced inother embodiments that depart from these specific details. In otherinstances, detailed descriptions of well-known methods, protocols,apparatuses, and circuits are omitted so as not to obscure thedescription of the present invention with unnecessary details.

The present invention is to be employed for detection of liner slips ina milking machine, which typically involves for each animal milkingunit, a clawpiece and a cluster of four teat cups connected to theclawpiece. Each teat cup has a rigid shell and an internal flexibleliner. This liner has a topmost mouthpiece and a body part inside theshell body. The liner extends through the bottom of the shell body as ashort milk tube. This tube is connected to clawpiece and thence, by wayof a long milk tube, to a source of steady vacuum. An annular space,between the teat cup shell and the teat cup liner, is connected to theclawpiece by a pulse tube and thence to a source of pulsating vacuum. Amilk meter may be attached to the downstream end of the long milk tube.

For milking, the four teat cups are placed around the animal's teats,the liner mouthpiece of each teat cup being fitted over the respectiveteat. The teat cups are held in position during the milking by adhesion,due to the steady vacuum applied for the milking. The pulsating vacuumapplied between the teat cup liner and shell causes the liner body todilate and contract again, thus promoting the flow of milk by simulatingsuckling. After completion of the milking, the teat cup cluster isremoved from the animal's teats, either manually or by automatic means.

During milking the liners may slip on the respective teat of the animaldue to air leaking past the teat and the liner. This unwantedphenomenon, named liner slip, may lead to udder infections, se e.g. J.O'Shea, Machine milking and mastitis, Bulletin of the internationaldairy federation, 215, Sec 2, 1987. Furthermore, if the liner slip islarge, the teat cup may slip off the teat, which may cause the entirecluster to fall off. Liner slips usually occur during the final part ofthe milking as the teat empties and the liner crawls up the teat.

Liner slips increases the airflow in the milking system, which causes avacuum drop. The airflow gets mixed with the milk, which may result in aturbulent milk flow whereby larger fat particles split into smallerparticles, which in turn might lead to shorter durability of fresh milk.More important, however, is that the turbulent air and milk dropletmixture may be propelled towards the teat ends and partially or totallypenetrate the teat canal. Hence, pathogens and other particles may beintroduced into healthy teats and cause irritation and udder infection,so called mastitis.

The vacuum drop in the liner may cause a rapid flow, called cross flow,of milk from the slipping liner into another liner, or a flow, calledjet flow, of mixed air and milk from the claw towards the teat tip.These flows may further impact the teats in an unwanted manner.

A liner slip may be defined as a slip due to a rather large and rapidair inlet, and should preferably not include small air inlets that moreor less continuously leaks past the teats (approximately 0.2 l/min) asthese latter air inlets are less critical for the teat health. Thepresent invention allows for user defined liner slips which may bealtered, as will be discussed further below.

It is possible to measure the liner slip as a vacuum drop in the systemsince this is a direct consequence of the increased airflow which aliner slip causes. However, the vacuum in the milking system is neverconstant; it varies due to different factors. The vacuum fluctuationsmay be divided into acyclic and cyclic fluctuations, of which the formerare mostly created by air admission into the system, transport of milkand underdimensioned milking installations, and the latter are caused byvolume changes beneath the teat tip as a consequence of the liner'sopening and closing. The size of the fluctuations depends on the milkflow.

The present invention comprises an apparatus for detecting liner slips,said apparatus comprises a pressure sensor located downstream of saidlong milk tube for continuously or discontinuously sensing the pressurein the system downstream of said long milk tube, and a detecting meansconnected to said sensor arranged for detecting a liner slip independence of a predetermined change in said sensed pressure.

FIG. 1 displays schematically an embodiment of such an apparatus fordetecting liner slips. The apparatus 1 comprises a pressure sensor ortransducer 3 located at the downstream end of the long milk tube (notshown). The pressure sensor 3 may be an absolute pressure sensor, but ispreferably a differential pressure sensor, that measures the differencebetween the pressure inside the long milk tube in the vicinity of itsdownstream end and the pressure outside said milk tube. The sensor mayfurther be a capacitive, deflection or magnetic sensor, but ispreferably a piezoresistive transmitter enclosed n a corrugated flushdiaphragm of steel filled with a non-compressible medium such as siliconoil.

The sensor 3 is preferably mounted by use of a T-piece of e.g. stainlesssteel (not shown). Said T-piece is mounted with its first end connectedto the downstream end of the long milk tube and its second end connectedto the steady vacuum, e.g. via a milk meter and further tubing. Thepressure sensor 3 is attached at the third end of the T-piece by virtueof an attaching means such as a nut.

The sensor 3 is connected to detecting means 5 via electric connection 7and arranged to transfer an electric output signal, for instance avoltage signal 0-5 V or a current signal 4-20 mA, preferablysubstantialy proportional to the sensed pressure, to detecting means 5.Said detecting means 5 typically comprises a micro-controller withappropriate software for detecting liner slips and for communication.The micro-controller is, in the illustrated embodiment, via connection 9further connected to an input/output means such as a PC 11 for, e.g.setting of parameters, and via connection 13 to a main controller 14 ofthe machine milking system for transferring of the number of detectedliner slips during the milking. In an alternative embodiment, theinput/output means 11 and/or the detecting means 5 may constituteintegral part(s) of the main machine milking controller system 13. Thearrows of communication lines 7, 9, 13 indicate the data transmittaldirection.

Considering next FIG. 2, which illustrates the vacuum level as afunction of time during a typical liner slip, the various inventivedetection criteria the liner slip detecting software in the detectingmeans may employ, are diagrammatically indicated. The vacuum levelexhibits three fast subsequent vacuum drops, of which, however, the twolatter follow the initial liner slip due to the pulsating action in thesystem. The latter vacuum drops are known as liner squawk and should notbe interpreted as liner slips.

The detecting criteria comprise the following ones, of which all maypreferably be employed simultaneously. However, the present invention isintended to cover any single criterion as well as any combination ofcriteria.

A rapidity criterion. A liner slip is detected if a vacuum drop occurs,which has a pressure derivative equal to or larger than a predeterminedlevel. This criterion may separate fast liner slips from slow cyclic andacyclic pressure variations. The rapidity criterion may preferably beimplemented as a predetermined pressure rise, e.g. 5-15 kPa, during ashort period of time, e.g. 0.1-0.2 seconds.

A magnitude criterion. A liner slip is detected if a vacuum drop occursthat has a magnitude equal to or larger than a predetermined level. Thiscriterion may separate large air inlets that occur at liner slips fromsmaller amounts of air that more or less continuously leak past theteat. The magnitude criterion may preferably be implemented as apredetermined pressure rise, e.g. 5-15 kPa. For practical reasons, themagnitude criterion may comprises that said predetermined pressure risehas to occur during a predetermined period of time, preferably 0.5-1seconds, which is considerably longer than the period of time associatedwith the rapidity criterion. The time should be set long enough todetect the entire pressure peak.

A time blocking criterion. Subsequent to a detected liner slip thedetecting is blocked during a predetermined blocking time, e.g. 5seconds, in order to separate liner slips from liner squawk. Thisblockage time implies that two detected liner slips always are separatedin time with at least this time.

A blocking at high-pressure criterion. If sensed pressure is above apredetermined level the detecting is blocked. This criterion ensuresthat detecting does not occur when no milking is performed, i.e. novacuum is supplied.

A blocking during cluster attachment criterion. The detecting is furtherblocked during a predetermined period of time for cluster attachment.This blocking time may be triggered by a vacuum supply sensed by thesensor and last for a number of seconds, e.g. 10 seconds. This criterionseparates the liner slips from fast and heavy vacuum fluctuations duringcluster attachment before milking is to proceed.

The number of detected liner slips during a predetermined period oftime, particularly one corresponding to one milking, is accumulated,preferably in the detecting means 5, whereafter this number is sent tothe main controller 14 for storing together with other data regardingthe milking. The criteria are set (and may be adjusted) through two-waycommunication between the detecting means 5 and the input/output means11. The various criteria are further discussed below in thisspecification in relation to the reporting of various experimentsperformed both in the laboratory and in the field.

Results from experiments as regards the location in the machine milkingsystem of the sensor of the inventive detection apparatus as comparedwith other locations will be discussed next.

It was found experimentally that a liner slip was always visible as adrastic drop of the vacuum level in the claw. Hence, experiments wereperformed in order to investigate how far downstream in the milkingmachine system a vacuum drop due to liner slip may be detected as it ispreferable to locate the sensor as far downstream as possible.

Experiments were performed in a 14 stall Herringbone parlour usingalternating pulsation with a pulsation rate of 60 pulsations per minute.The pressure was measured simultaneously at three different points inthe system; in the claw, at the end of a standard long milk tube, justbefore inlet to a milk meter and in the upper part of the milk meterright behind the inlet. Three miniature transducers with semiconductorsensors (model P10EZ from Viggo-Spectramed) were used. At the end of thelong milk tube the sensor was connected to a syringe that was insertedthrough the rubber material. The sensor signals were recorded and savedusing a PC with appropriate designed software.

During the milking of three different cows, several liner slips wereinduced by pressing at the teat Just above the mouthpiece. During afourth milking a true liner slip occurred. The pressure recordings fromthe four milkings were studied in detail and the number of liner slipsdistinguishable from the normal vacuum variations at the end of the longmilk tube and in the milk meter were compared with the number of linerslips distinguishable in the claw. Examples of the three differentvacuum levels are diagrammatically shown in FIG. 3.

The vacuum drops due to liner slips were analyzed and the results arepresented in Table 1. Each liner slip that was distinguishable in theclaw was also visible as a drop in the vacuum level at the end of thelong milk tube. This was not always the case in the milk meter, whereonly 45-75% of the induced liner slips seen in the claw wasdistinguishable.

According to the results, it is seen that a reliable liner slipdetecting apparatus may have its sensor located at the end of the longmilk tube. There are many advantages in locating a sensor at thisposition instead of in the claw; a larger sensor can be used, the sensorwill be better protected against mechanical damage and no wires to theclaw will be needed. Locating the sensor in the milk meter would providethe same advantages; however, this is not a good alternative in thepresent configuration since some of the liner slips will not bedetected. In other circumstances, however, the sensor may equally wellbe located in the milk meter or even further downstream.

TABLE 1 Number of induced liner slips as distinguished in the claw, atthe end of the long milk tube, and in the milk meter, respectively. Thepercentages of the number of distinguished liner slips at the two latterpoints as compared with the number of distinguished liner slips in theclaw are shown within parenthesis. No. of No. of distinguishable No. ofdistinguishable liner slips distinguishable liner slips at the end linerslips Cow in the claw of the long milk tube in the milk meter 1 14 14(100%)  9 (64%) 2 16 16 (100%) 12 (75%) 3 29 29 (100%) 13 (45%)

In the experiment performed the normal vacuum variations in the clawwere cyclic with a period of approximately 0.5 seconds. The magnitude ofthe fluctuations in the claw depends on the milk flow; a large milk flowgives rise to large vacuum variations, sometimes as large as 10 kPa. Atthe end of the long milk tube the variations were smaller and lessregular. The magnitude of the variations was usually less than 5 kPa,but occasionally large drops with a magnitude of up to 8 kPa could benoted. These large vacuum fluctuations could have a fall time of lessthan 0.2 seconds.

Results from experiments as regards the effects of the settings of theinventive rapidity and magnitude criteria on the performance of thedetection apparatus according to the invention will be considered next.

In the setup as used the vacuum level at the end of the long milk tubevaried during a milking as follows.

Before milking started, vacuum was applied to the system, but theentrance to the long milk tube was at this time blocked by a rubberseal. Hence, the cluster and the long milk tube were kept at atmosphericpressure. Just before the cluster was attached the user opened therubber seal (e.g. by pressing a button), whereby vacuum was applied tothe long milk tube and the cluster. If two different vacuum levels wereemployed (one low, e.g. 33 kPa, in the beginning and at the end of themilking and one higher, e.g. 50 kPa, in the middle part of the milking),the lower one was applied.

When the cluster was attached to the udder, the vacuum level droppeddrastically several times due to large amounts of air that entered thesystem. When the cluster was properly attached, the vacuum levelstabilized and stayed at the lower level within normal cyclicvariations.

The higher vacuum level was then applied, i.e. when the milk flowreached a certain limit, e.g. 100-500 g/min. If no liner slips orfall-offs occurred, the vacuum level stayed stable within the normalvariations until the milk flow decreased below the above mentionedlimit. A this point, the vacuum level was reduced to the lower vacuumlevel. A certain time after the vacuum transition from high to lowvacuum, the rubber seal disconnected the long milk tube from the vacuumsupply, the cluster was automatically detached and the vacuum level inthe cluster and the long milk tube dropped to atmospheric pressure.

In order to prevent the milk, remaining in the cluster after removal,from leaking out on the floor, vacuum (e.g. the higher level) wasapplied again during a few seconds and the milk was sucked out. However,sometimes there was a valve in the claw used to close the outlet to thelong milk tube in case of fall-off. This prevented dirt from beingsucked into the milk tank. If this valve was used it also prevented themilk from being sucked out after take-off. It acted as a seal betweenthe long milk tube and the claw, so that between milkings the vacuumremained in the long milk tube, whereas there was atmospheric pressurein the claw. If the valve was locked in open position, the vacuum levelin the long milk tube also fell to atmospheric pressure after a fewseconds of vacuum.

In order to evaluate rapidity and magnitude criteria, experiments wereperformed with various different settings, the results of which areshown in Table 2. For most values of the rapidity and magnitude criteriathe liner slip detecting apparatus worked excellently. When lowparameter values (5-6 kPa) were used, many normal vacuum variations weredetected as false positives, i.e. they were incorrectly detected asliner slips. This was not surprising, since it had been seen before thatnormal vacuum variations in the laboratory setup were very large. Asexpected, too large parameter values did not allow detection of all airinlets.

In order to test the blockage of further detection after the occurrenceof a liner slip, the blockage time parameter was altered, and it wasascertained that after the detection of a liner slip, further detectionwas blocked during the time chosen.

TABLE 2 Laboratory test results of the inventive liner slip detectionapparatus. The number of liner slips as correctly and incorrectlydetected, respectively, for different settings of the detection criteriarapidity and magnitude are shown. The percentages of the number ofcorrectly detected liner slips as compared with the number of inducedliner slips are shown within parenthesis. Values of criteria High flow,vacuum level 50 kPa Low flow, vacuum level 33 kPa Rapidity Magnitude No.of No. No. false No. of No. No. false (kPa/0.2 s) (kPa) air inletsdetected positives air inlets detected positives  5  5 20 20 (100%) 2320 20 (100%) 21  5  8 20 20 (100%)  0 20 20 (100%)  0  6  6 20 20 (100%) 5 20 20 (100%)  3  6  8 20 20 (100%)  0 20 20 (100%)  0  8 10 20 20(100%)  0 20 20 (100%)  0  8 15 20 10 (50%)   0 20 20 (100%)  0  8 20 203 (15%)  0 20 20 (100%)  0 10 10 20 20 (100%)  0 20 20 (100%)  0 10 1220 17 (85%)   0 20 18 (90%)   0

The liner slip detecting apparatus was also tested during four milkingsin a Herringbone parlour. Several combinations of the rapidity andmagnitude criteria were tested.

The normal vacuum variations were much smaller than in the laboratory.Parameter values equal to or greater than 5 kPa in 0.2 seconds and 5kPa, respectively, were used without detecting any false positives, butif they were further lowered, several normal vacuum variations weredetected as liner slips. However for the indicated parameter values, thetransition from high to low vacuum was occasionally detected as a linerslip. Hence, these transitions may be faster than 5 kPa in 0.2 seconds.The value of the rapidity criteria must be increased to 6 kPa in 0.2seconds in order to avoid vacuum transitions from being detected asliner slips.

The value of the magnitude criterion should be higher than the vacuumvalue of the rapidity criterion. Therefore, it is not ideal to use arapidity criterion of 6 kPa or higher in 0.2 seconds since this wouldrestrict the user's possibilities to detect small liner slips.Consequently, the rapidity criterion should be modified by decreasingthe time, e.g. to 0.1 seconds, instead of increasing the pressure value.

Using criteria of 5 kPa in 0.1 seconds and 5-8 kPa, respectively, wasfound to be optimal values. When a rapidity criterion of 5 kPa in 0.1seconds is used, the risk of detecting vacuum transitions as liner slipsis very small. A magnitude criterion value of 7-8 kPa prevents normalvacuum variations from being detected as liner slips. Very small airinlets could be missed by using these parameter values, but it all comesdown to the subtle question of how to define a liner slip. The risk ofdetecting normal vacuum variations as liner slips is increased as themagnitude criterion value is decreased.

The above stated numerical values are off course equipment dependent andshall therefore only be taken as illustrative examples.

If the user wants to make sure that no normal vacuum variations aredetected, the magnitude criterion value should be increased further, andif he wants to perform very accurate measurements of small liner slips,the magnitude of the normal vacuum variations at the end of the longmilk tube (or elsewhere where the sensor is located) should bedetermined before and used when setting the criteria values.

Finally, FIG. 4 displays four examples of strip chart recordings of thevacuum level in the claw of the milking machine during occurrence ofliner slips, all of which were detected as liner slips by the inventiveliner slip detecting apparatus.

A further embodiment of the present invention (not illustrated)comprises the implementation of the liner slip detecting apparatus in amilking machine system that slightly deviates from the system describedabove. Here, the milking machine system comprises, for each milkingunit, teat cups, each having a shell body and an internal flexibleliner, said internal flexible liner comprising a mouthpiece and a bodypart, wherein each liner extends through the bottom of the respectiveshell body and is connected, by way of a respective long milk tube, to asource of steady vacuum, while the respective annular space, between theshell body and the liner, is connected to a source of pulsating vacuum.Each long milk tube may be connected to a respective shut off andregulator valve and then, by way of a further tube, to a respective milkmeter for measuring the milk yield from each teat individually. Theoutput from each milk meter is preferably connected to a further milkmeter for measuring the weight of the milk, thus giving the total milkyield for all teats. Said milk meter is preferably mounted in immediateconnection to the milk receiver.

The liner slip detecting apparatus comprises a pressure sensor locateddownstream of said long milk tubes (e.g. before said valves, in betweenthe valves and the individual milk meters, or after said milk meters)for continuously or discontinuously sensing the pressure in the systemdownstream of said long milk tubes, and a detecting means connected tosaid sensor arranged for detecting a liner slip in dependence of apredetermined change in said sensed pressure.

Preferably, a pressure sensor is located at the end or furtherdownstream of each long milk tube for sensing the individual pressure atthe end of each long milk tube, wherein the detecting means is arrangedfor detecting a liner slip in dependence of a predetermined change inone of each sensed pressures and for identifying the slipping liner, byway of identifying said one of each sensed pressures.

The detecting apparatus may otherwise be implemented as describedelsewhere in this detailed description of embodiments e.g., with thedetecting means arranged for detecting a liner slip if saidpredetermined pressure change fulfills a rapidity criterion, and/or amagnitude criterion.

In summary, a reliable and high-quality method and apparatus isdisclosed for detecting and counting of liner slips that occur duringmilking using various different milking machines.

The apparatus comprises a pressure sensor located downstream of the longmilk tube(s) for continuously or discontinuously sensing the pressure inthe system downstream of said long milk tube(s), and a detecting meansconnected to said sensor arranged for detecting liner slips independence of predetermined changes in said sensed pressure.

The invention offers, inter alia, the following features and advantages.

The apparatus is suited for the extreme environment that a milkingmachine may comprise. The most exposed part of the apparatus is thevacuum sensor preferably located at the end of the long milk tube(s),which will be in contact with milk, hot water and washing detergents.

There are many advantages in locating a sensor at this position insteadof further upstream such as in the claw; a larger sensor can be used,the sensor will be better protected against mechanical damage and nowires to the claw will be needed. This will particularly allow forlong-term operation of the liner slip detecting apparatus.

The method will be totally automatic. Once the measuring system has beeninstalled, liner slip detection will be performed without any furtherinvolvement from the milking staff.

The invention allows for automatic data input to a central database ofthe machine milking system.

The detecting does not affect the farmer's routines or daily work.

The sensor will be cleaned together with the rest of the system.

The apparatus is easy to use. No calibration of the apparatus is neededwhen it once has been installed, unless the user wants to perform veryaccurate measurements of small liner slips.

The installation of the detecting apparatus includes connection of aT-piece at the end of the long milk tube(s), connection of cables to acontroller board and from the controller board to a communicationssystem, and attaching said board to a wall or the like, tasks easilyperformed by a technician without special training.

The apparatus offers a very flexible operation as it actually allows theuser to define a liner slip by the setting of the various criteria.

The apparatus may be manufactured to a very low cost.

In the last depicted embodiment, by localizing a pressure sensor at theend of each long milk tube, it is even possible to identify at whichteat cup the liner slip occurs.

It will be obvious that the invention may be varied in a plurality ofways. Such variations are not to be regarded as a departure from thescope of the invention. All such modifications as would be obvious toone skilled in the art are intended to be included within the scope ofthe appended claims.

What is claimed is:
 1. A method for detecting liner slips in a milkingmachine system having at least one milking unit, each of said at leastone milking unit including a clawpiece and a cluster of teat cupsconnected to the clawpiece, wherein each teat cup has a shell body andan internal flexible liner, said liner comprising a mouthpiece and abody part, whereby the liner extends through the bottom of the shellbody as a short milk tube and is connected to the clawpiece and further,by way of a long milk tube, to a source of steady vacuum, an annularspace located between the teat cup shell body and the teat cup linerbeing connected to the clawpiece by a pulse tube and further to a sourceof pulsating vacuum, said method including the steps of: sensing thepressure of the milk-air mixture in the system downstream of said longmilk tube, and detecting a liner slip in dependence of a predeterminedchange in said sensed pressure.
 2. The method as claimed in claim 1,including detecting a liner slip if said predetermined pressure changefulfills a rapidity criterion.
 3. The method as claimed in claim 2,including choosing the rapidity criterion as predetermined pressure riseduring a short period of time.
 4. The method as claimed in claim 1,including detecting a liner slip if said predetermined pressure changefulfills a magnitude criterion.
 5. The method as claimed in claim 4,including choosing the magnitude criterion as a predetermined pressurerise.
 6. The method as claimed in claim 5, wherein the magnitudecriterion comprises that said predetermined pressure rise occurs duringa predetermined period of time.
 7. The method as claimed in claim 1,including blocking the detecting during a predetermined blocking timesubsequent to a detected liner slip.
 8. The method as claimed in claim1, including blocking the detecting when the sensed pressure is above apredetermined level.
 9. The method as claimed in claim 1, includingblocking the detecting during a predetermined period of time for clusterattachment.
 10. The method as claimed in claim 1, including accumulatingthe number of detected liner slips during a predetermined period oftime.
 11. The method as claimed in claim 1 wherein the sensing stepincludes continuously sensing the pressure in the system downstream ofsaid long milk tube.
 12. The method as claimed in claim 1 wherein thesensing step includes discontinuously sensing the pressure in the systemdownstream of said long milk tube.
 13. An apparatus for detecting linerslips in a milking machine having at least one milking unit, each atleast one milking unit having a clawpiece and a cluster of teat cupsconnected to the clawpiece, wherein each teat cup has a shell body andan internal flexible liner, said liner comprising a mouthpiece and abody part, whereby the liner extends through the bottom of the shellbody as a short milk tube and is connected to the clawpiece and further,by way of a long milk tube, to a source of steady vacuum, an annularspace located between the teat cup shell body and the teat cup linerbeing connected to the clawpiece by a pulse tube and further to a sourceof pulsating vacuum, said apparatus comprising: a pressure sensorlocated downstream of said long milk tube for continuously ordiscontinuously sensing the pressure of the milk-air mixture in thesystem downstream of said long milk tube, and a detecting meansconnected to said sensor arranged for detecting a liner slip independence of a predetermined change in said sensed pressure.
 14. Theapparatus as claimed in claim 13, wherein the detecting means isarranged for detecting a liner slip if said predetermined pressurechange fulfills a rapidity criterion.
 15. The apparatus as claimed inclaim 14, wherein the rapidity criterion is a predetermined pressurerise during a short period of time.
 16. The apparatus as claimed inclaim 13, wherein the detecting means is arranged for detecting a linerslip if said predetermined pressure change fulfills a magnitudecriterion.
 17. The apparatus as claimed in claim 16, wherein themagnitude criterion is a predetermined pressure rise.
 18. The apparatusas claimed in claim 13, wherein the apparatus is arranged for blockingthe detecting during a predetermined blocking time subsequent to adetected liner slip.
 19. The apparatus a claimed in claim 13, whereinthe apparatus is arranged for blocking the detecting when the sensedpressure is above a predetermined level.
 20. The apparatus as claimed inclaim 13, wherein the apparatus is arranged for accumulating the numberof detected liner slips during a predetermined period of time.
 21. Theapparatus as claimed in claim 13, including a T-piece having a first endconnected to the downstream end of the long milk tube, a second endconnected to the steady vacuum, and a third end, whereby the sensor isattached at the third end of the T-piece by virtue of an attachingmeans.
 22. The apparatus as claimed in claim 13, wherein the apparatusfurther comprises means for adjusting the predetermined pressure change.23. A method for detecting liner slips in a milking machine systemhaving at least one milking unit, each of said at least one milking unitincluding a plurality of teat cups, each of said teat cups having ashell body and an internal flexible liner, said internal flexible linercomprising a mouthpiece and a body part, wherein each liner extendsthrough the bottom of the respective shell body and is connected, by wayof a respective long milk tube, to a source of steady vacuum, and arespective annular space, located between the shell body and the linerbeing connected to a source of pulsating vacuum, said method comprisingthe steps of: sensing the pressure in the system downstream of each ofsaid long milk tubes, detecting a liner slip in dependence of apredetermined change in one of each sensed pressure, and furtheridentifying a slipping liner by way of identifying said one of eachsensed pressures.
 24. The method as claimed in claim 23, includingdetecting a liner slip if said predetermined pressure change fulfills arapidity criterion.
 25. The method as claimed in claim 23, includingblocking the detecting during a predetermined blocking time subsequentto a detected liner slip.
 26. The method as claimed in claim 23 whereinthe sensing step includes continuously sensing the pressure in thesystem downstream of said long milk tube.
 27. The method as claimed inclaim 23 wherein the sensing step includes discontinuously sensing thepressure in the system downstream of said long milk tube.
 28. The methodas claimed in claim 23 including detecting a liner slip if saidpredetermined pressure change fulfills a magnitude criterion.
 29. Anapparatus for detecting liner slips in a milking machine system havingat least one milking unit, each at least one milking unit having aplurality of teat cups, each teat cup having a shell body and aninternal flexible liner, said internal flexible liner comprising amouthpiece and a body part, wherein each liner extends through thebottom of the respective shell body and is connected, by way of arespective long milk tube, to a source of steady vacuum, while therespective annular space, between the teat cup shell body and the liner,is connected to a source of pulsating vacuum, said apparatus comprising:a plurality of pressure sensors located downstream of each of said longmilk tubes for continuously or discontinuously sensing the pressure inthe system downstream of each of said long milk tubes, and a detectingmeans connected to said sensor arranged for detecting a liner slip independence of a predetermined change in one of each said sensed pressureand for identifying a slipping liner by way of identifying said one ofeach sensed pressures.
 30. The apparatus as claimed in claim 29 whereinthe detecting means is arranged for detecting a liner slip if saidpredetermined pressure change fulfills a rapidity criterion.
 31. Theapparatus as claimed in claim 29, wherein the apparatus is arranged forblocking the detecting during a predetermined blocking time subsequentto a detected liner slip.
 32. The apparatus as claimed in claim 29wherein the detecting means is arranged for detecting a liner slip ifsaid predetermined pressure change fulfills a magnitude criterion.
 33. Amethod for detecting liner slips in a milking machine system having atleast one milking unit, each of said at least one milking unit includinga clawpiece and a cluster of teat cups connected to the clawpiece,wherein each teat cup has a shell body and an internal flexible liner,said liner comprising a mouthpiece and a body part, whereby the linerextends through the bottom of the shell body as a short milk tube and isconnected to the clawpiece and further, by way of a long milk tube, to asource of steady vacuum, an annular space located between the teat cupshell body and the teat cup liner being connected to the clawpiece by apulse tube and further to a source of pulsating vacuum, said methodincluding the steps of: sensing the pressure in the system at thedownstream end of said long milk tube, and detecting a liner slip independence of a predetermined change in said sensed pressure.
 34. Anapparatus for detecting liner slips in a milking machine having at leastone milking unit, each at least one milking unit having a clawpiece anda cluster of teat cups connected to the clawpiece, wherein each teat cuphas a shell body and an internal flexible liner, said liner comprising amouthpiece and a body part, whereby the liner extends through the Bottomof the shell body as a short milk tube and is connected to the clawpieceand further, by way of a long milk tube, to a source of steady vacuum,an annular space located between the teat cup shell body and the teatcup liner being connected to the clawpiece by a pulse tube and furtherto a source of pulsating vacuum, said apparatus comprising: a pressuresensor located at the downstream end of said long milk tube forcontinuously or discontinuously sensing the pressure in the system atthe downstream end of said long milk tube, and a detecting meansconnected to said sensor arranged for detecting a liner slip independence of a predetermined change in said sensed pressure.